Comparative Evaluation of Urine, Sputum, and BALF for Human Microplastic Exposure Monitoring Using a Multicriteria Decision Framework.

Microplastic (MP) contamination in human biological systems has become a global health concern. However, the selection of the most suitable matrix for biomonitoring remains an open area of investigation. This study evaluates three biological matrices-urine, sputum, and bronchoalveolar lavage fluid (BALF)-for their suitability in MP detection and monitoring. Using data collated from a recent observational study (30 patients) and peer-reviewed literature, we assessed detection sensitivity, polymer diversity, sample availability, and practical feasibility via a multicriteria decision analysis (MCDA) framework inspired by the analytic hierarchy process (AHP). Results showed that sputum exhibited the highest median MP concentration (9.4 particles/mL) and BALF showed the greatest polymer diversity (6 polymer types), while urine showed the lowest levels (2.7 particles/mL). The composite MCDA scores ranked urine highest (26/35) for population studies due to its noninvasiveness and reproducibility, followed by sputum (25/35) for respiratory exposure assessment and BALF (21/35) for deep-lung mechanistic studies. We conclude that a matrix-specific strategy is essential for advancing human MP biomonitoring.